Internal Flux-Core Solder Preforms for Uniform Reflow Wetting

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Solution Overview

Problem

Conventional solder tubes with exterior flux coatings face issues such as difficulty in achieving uniform flux distribution, flux obstruction, tacky surfaces, chipping, and dust formation, leading to production downtime and quality control challenges.

Innovation Solution

Solder preforms with an internal flux core containing a thermochromic indicator, which flows out during reflow soldering, providing a visual temperature indication and improving wetting without the need for exterior flux coatings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If an exterior flux coating is applied to the solder tube, then flux is provided to facilitate soldering, but uniform flux distribution is difficult to achieve and surface issues such as tackiness, chipping, and dust formation occur

Engineering Contradiction:

Improveflux contentVSAvoidflux distribution uniformity

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional approach by moving the flux coating from the exterior surface to an internal core. Instead of applying flux externally where it causes surface defects, the flux is embedded within the solder alloy body as a core, which then flows out through openings during reflow soldering to provide the necessary fluxing action without the associated surface problems.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The flux core is nested within the solder alloy body, with the flux contained inside a core structure that is embedded in the solder material. This nested configuration allows the flux to be delivered from the interior through openings in the solder tube, providing flux where needed while maintaining a clean exterior surface free from coating defects.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Ease of operation

If an exterior flux coating with thermochromic dye is applied, then visual temperature verification is provided, but the coating adds complexity and surface defects

Engineering Contradiction:

Improvevisual temperature indicationVSAvoidcoating process complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent combines the flux and thermochromic indicator into a single integrated core structure. Instead of applying separate exterior coatings for fluxing and temperature indication, both functions are merged into one internal component that delivers both flux and visual temperature verification simultaneously through the same openings in the solder tube.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The thermochromic indicator is extracted from the exterior coating and placed inside the flux core. This extraction eliminates the need for complex multi-layer exterior coatings while maintaining the visual temperature indication function, as the thermochromic material within the core provides color change indication as the flux flows out during reflow soldering.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If exterior flux coating is used, then soldering facilitation is achieved, but production downtime increases due to quality control challenges

Engineering Contradiction:

Improvesolder joint qualityVSAvoidproduction efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The internal flux core provides self-contained flux delivery and temperature indication without requiring external application or monitoring. The core automatically flows out through the solder tube openings during reflow soldering, providing both fluxing action and visual temperature verification in a self-service manner that eliminates the need for separate quality control checks and reduces production downtime.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The internal flux core design allows for higher flux content, consistent dimensions, eliminates surface issues, and reduces production downtime by preventing flux dust formation, resulting in improved solder joint formation and increased production efficiency.

Implementation Method 1

a thermochromic indicator, wherein during reflow soldering, the flux core comprising the thermochromic indicator is configured to flow out of the at least one opening of the solder alloy. During reflow soldering, the thermochromic indicator may be configured to lose color as the solder alloy approaches its peak reflow soldering temperature.

Methodology Applied

Scientific EffectThermochromism: Thermochromism

Data Source

PatentUS11602808B2Solder preform with internal flux core including thermochromic indicator

Publication Date: 2023.03.14 INDIUM CORP

AI summary

Some implementations of the disclosure are directed to a solder preform, comprising: a solder alloy body, the solder alloy body comprising at least one opening; and a flux core embedded in the solder alloy body, the flux core comprising a thermochromic indicator, wherein during reflow soldering, the flux core comprising the thermochromic indicator is configured to flow out of the at least one opening of the solder alloy.